In the SJI catalog, (Re: 43rd edition, page 123) the length of the joist is defined as
L = (span - 0.33) in feet.
Since we deal with the span in Ram Steel, we simply adjust the values in the table by the 0.33' value to get back to the SJI definition of length. Hence the tabulated value for 59.67' in RAMSJI.jst matches the SJI values for 60'.